The thermal decomposition behavior of gel precursor, the structure, morphology and electrochemical properties of NiO thin films prepared by sol-gel process were characterized by thermogravimetric/differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and constant current charge-discharge techniques. The results show that the gel precursor completely decomposes and gradually forms the nanocrystalline NiO at 450°C during the sintering. The NiO thin film is smooth, uniform and free of cracks drying at 200°C as pretreatment and sintering at a low temperature rise rate. The structure of NiO films sintered at 500°C for 2h becomes integrity, whose discharge capacity after 20 cycles remains at 714mAh/g. It is promising to be used in Li-ion battery for great initial specific capacity and well cycle performances.